The broad objective of this research is to study the changes that occur in protein metabolism as a result of exercise and to establish the underlying biochemical mechanisms which bring about these changes. In research already completed, we have clearly established that an acute bout of excerise (either running or swimming) causes a decrease in the rate of muscle protein synthesis and increased rates of protein degradation in muscle and liver. Preliminary evidence from our lab and reports other investigators suggest that an acute exercise bout also increases the rate of amino acid oxidation. During the next granting period we propose to further study the effect of an acute exercise bout of protein synthesis, protein degradation and amino acid oxidation. To determine mechanisms involved in the decrease in protein synthesis in muscle, we plan to determine the effect of exercise on the various components of protein synthesis: charging of t-RNA, initiation of peptide synthesis and peptide elongation. An investigation of the effect of exercise on protein degradation will center on the increase in lysosomal "fragility" that we have observed. A number of pharmacological agents known to stabilize lysosomal membranes and/or inhibit lysosomal proteases will be used to determine whether the increased protein degradation can be blocked. Experiments are planned which will establish with certainty whether amino acid oxidation is increased during exercise. In addition, several individual enzymes involved in amino acid metabolism will be assayed in an attempt to determine the mechanism(s) underlying an altered rate of amino acid utilization. In addition to studying the mechanisms that cause the alterations in protein synthesis, protein degradation, and amino acid oxidation during an acute exercise bout, we also plan to study the alterations that occur in protein synthesis and breakdown during the recovery phase after exercise.